There should be a single GC excludes file (#3)

Author: chrisseaton

test/excludes/_third_party_heap/TestGC.rb

@@ -29,4 +29,8 @@
 exclude :test_vm_object, "no gc implemented yet"
 exclude :test_exception_in_finalizer_procs, "no gc implemented yet"
 exclude :test_exception_in_finalizer_method, "no gc implemented yet"
-exclude :test_object_ids_never_repeat, "no gc implemented yet"
+exclude :test_object_ids_never_repeat, "no gc implemented yet"
+exclude :gc_mark_begin, "no gc implemented yet"
+exclude :gc_mark_end, "no gc implemented yet"
+exclude :gc_sweep_begin, "no gc implemented yet"
+exclude :gc_sweep_end, "no gc implemented yet"